FIG. 6 is a block diagram showing a conventional control apparatus. The control apparatus is used for a vehicle. As shown in FIG. 6, the control apparatus has a momentary switch SW and a microcomputer 101. The microcomputer 101 switches the control state of a to be-controlled object (for example, rear fog lamp) between a first control state (for example, state in which function is ON) and a second control state (for example, state in which function is OFF) each time the momentary switch SW is operated. More specifically, when the momentary switch SW is operated, the microcomputer 101 discriminates whether the operation is a first operation to turn on the function or a second operation to turn off the function. Each time the momentary switch SW is operated, as shown in FIG. 7, the microcomputer 101 switches the control state of a rear fog lamp 3 ON, OFF, ON, OFF, . . . through a switching transistor Tr. Therefore the microcomputer 101 controls the rear fog lamp 3 by always storing the operation state, where the function is ON by a first operation or where the function is OFF by a second operation, of the momentary switch SW.
The rear fog lamp 3, the transistor Tr, and an ignition switch 5 are mounted in series with a path 7. One end of the path 7 is connected to a power source line and other end is connected to the ground. Thus when the transistor Tr is turned on and off under the control of the microcomputer 101, with the ignition switch ON, the rear fog lamp 3 is turned on and off.
However, in the conventional control apparatus, when the supply of electric power to the microcomputer 101 is terminated because of a temporary (or instantaneously) interruption of supply of the electric power such as a battery exchange, disconnection of a power source line or some factor, information on the operation state of the momentary switch SW stored by the microcomputer 101 disappears. Thus, when the supply of the electric power is resumed, it is necessary to reset the control state of the rear fog lamp 3 to an initial state, for example, an off state.
Therefore when the supply of the electric power to the microcomputer 101 is interrupted instantaneously at a time T when the rear fog lamp 3 is ON as shown in FIG. 7, the microcomputer 101 resets (release of ON state) the control state of the rear fog lamp 3 to the OFF state. After the supply of the electric power is resumed, the rear fog lamp 3 is kept in the OFF state. To turn on the rear fog lamp 3, it is necessary to operate the momentary switch.